The present invention generally relates to processes for making polymeric microparticles or microspheres containing an alpha-2 adrenergic receptor agonist and use thereof to treat an ocular condition.
Ocular hypotensive agents are useful in the treatment of a number of various ocular hypertensive conditions, such as post-surgical and post-laser trabeculectomy ocular hypertensive episodes, glaucoma, and as presurgical adjuncts.
Glaucoma is a disease of the eye characterized by increased intraocular pressure. On the basis of its etiology, glaucoma has been classified as primary or secondary. For example, primary glaucoma in adults (congenital glaucoma) may be either open-angle or acute or chronic angle-closure. Secondary glaucoma results from pre-existing ocular diseases such as uveitis, intraocular tumor or an enlarged cataract.
The underlying causes of primary glaucoma are not yet known. The increased intraocular tension is due to the obstruction of aqueous humor outflow. In chronic open-angle glaucoma, the anterior chamber and its anatomic structures appear normal, but drainage of the aqueous humor is impeded. In acute or chronic angle-closure glaucoma, the anterior chamber is shallow, the filtration angle is narrowed, and the iris may obstruct the trabecular meshwork at the entrance of the canal of Schlemm. Dilation of the pupil may push the root of the iris forward against the angle, and may produce pupillary block and thus precipitate an acute attack. Eyes with narrow anterior chamber angles are predisposed to acute angle-closure glaucoma attacks of various degrees of severity.
Secondary glaucoma is caused by any interference with the flow of aqueous humor from the posterior chamber into the anterior chamber and subsequently, into the canal of Schlemm. Inflammatory disease of the anterior segment may prevent aqueous escape by causing complete posterior synechia in iris bombe and may plug the drainage channel with exudates. Other common causes are intraocular tumors, enlarged cataracts, central retinal vein occlusion, trauma to the eye, operative procedures and intraocular hemorrhage.
Considering all types together, glaucoma occurs in about 2% of all persons over the age of 40 and may be asymptotic for years before progressing to rapid loss of vision. In cases where surgery is not indicated, topical beta-adrenoreceptor antagonists have traditionally been the drugs of choice for treating glaucoma.
Prostaglandins were earlier regarded as potent ocular hypertensives; however, evidence accumulated in the last two decades shows that some prostaglandins are highly effective ocular hypotensive agents and are ideally suited for the long-term medical management of glaucoma. (See, for example, Starr, M. S. Exp. Eye Res. 1971, 11, pp. 170-177; Bito, L. Z. Biological Protection with Prostaglandins Cohen, M. M., ed., Boca Raton, Fla., CRC Press Inc., 1985, pp. 231-252; and Bito, L. Z., Applied Pharmacology in the Medical Treatment of Glaucomas Drance, S. M. and Neufeld, A. H. eds., New York, Grune & Stratton, 1984, pp. 477-505). Such prostaglandins include PGF2α, PGF1α, PGE2, and certain lipid-soluble esters, such as C1 to C5 alkyl esters, e.g. 1-isopropyl ester, of such compounds.
In U.S. Pat. No. 4,599,353 certain prostaglandins, in particular PGE2 and PGF2α and the C1 to C5 alkyl esters of the latter compound, were reported to possess ocular hypotensive activity and were recommended for use in glaucoma management.
Although the precise mechanism is not yet known, recent experimental results indicate that the prostaglandin-induced reduction in intraocular pressure results from increased uveoscleral outflow [Nilsson et al., Invest. Ophthalmol. Vis. Sci. 28(suppl), 284 (1987)].
The isopropyl ester of PGF2α has been shown to have significantly greater hypotensive potency than the parent compound, which was attributed to its more effective penetration through the cornea. In 1987, this compound was described as “the most potent ocular hypotensive agent ever reported.” [See, for example, Bito, L. Z., Arch. Ophthalmol. 105, 1036 (1987), and Siebold et al., Prodrug 5, 3 (1989)].
Whereas prostaglandins appear to be devoid of significant intraocular side effects, ocular surface (conjunctival) hyperemia and foreign-body sensation have been consistently associated with the topical ocular use of such compounds, in particular PGF2α and its prodrugs, e.g. its 1-isopropyl ester, in humans. The clinical potential of prostaglandins in the management of conditions associated with increased ocular pressure, e.g. glaucoma, is greatly limited by these side effects.
Certain prostaglandins and their analogs and derivatives, such as the PGF2α derivative latanoprost, sold under the trademark Xalatan®, have been established as compounds useful in treating ocular hypertension and glaucoma. However, latanoprost, the first prostaglandin approved by the United States Food And Drug Administration for this indication, is a prostaglandin derivative possessing the undesirable side effect of producing an increase in brown pigment in the iris of 5-15% of human eyes. The change in color results from an increased number of melanosomes (pigment granules) within iridial melanocytes. See e.g., Watson et al., Ophthalmology 103:126 (1996). While it is still unclear whether this effect has additional and deleterious clinical ramifications, from a cosmetic standpoint alone such side effects are undesirable.
Certain phenyl and phenoxy mono, tri and tetra prostaglandins and their 1-esters are disclosed in European Patent Application 0,364,417 as useful in the treatment of glaucoma or ocular hypertension.
In a series of United States patent applications assigned to Allergan, Inc. prostaglandin esters with increased ocular hypotensive activity accompanied with no or substantially reduced side-effects are disclosed. U.S. patent application Ser. No. 386,835 (filed Jul. 27, 1989), relates to certain 11-acyl-prostaglandins, such as 11-pivaloyl, 11-acetyl, 11-isobutyryl, 11-valeryl, and 11-isovaleryl PGF2α. Intraocular pressure reducing 15-acyl prostaglandins are disclosed in U.S. Ser. No. 357,394 (filed May 25, 1989). Similarly, 11,15-9,15- and 9,11-diesters of prostaglandins, for example 11,15-dipivaloyl PGF2α are known to have ocular hypotensive activity. See U.S. Ser. No. 385,645 filed Jul. 27, 1990,. now U.S. Pat. No. 4,494,274; 584,370 which is a continuation of U.S. Ser. No. 386,312, and U.S. Ser. No. 585,284, now U.S. Pat. No. 5,034,413 which is a continuation of U.S. Ser. No. 386,834, where the parent applications were filed on Jul. 27, 1989.
Woodward et al U.S. Pat. Nos. 5,688,819 and 6,403,649 disclose certain cyclopentane heptanoic acid, 2-cycloalkyl or arylalkyl compounds as ocular hypotensives. These compounds, which can properly be characterized as hypotensive lipids, are effective in treating ocular hypertension.
As one example, the prostamide analog, bimatoprost, has been discovered to be effective in reducing intraocular pressure possibly by increasing the aqueous humour outflow of an eye (Woodward et al., AGN 192024 (Lumigan®): A Synthetic Prostamide Analog that Lowers Primate Intraocular Pressure by Virtue of Its Inherent Pharmacological Activity, ARVO 2002; (CD-ROM):POS; Chen et al., Lumigan®: A Novel Drug for Glaucoma Therapy, Optom In Pract, 3:95-102 (2002); Coleman et al., A 3-Month Randomized Controlled Trial of Bimatoprost (LUMIGAN) versus Combined Timolol and Dorzolamide (Cosopt) in Patients with Glaucoma or Ocular Hypertension, Ophthalmology 110(12): 2362-8 (2003); Brubaker, Mechanism of Action of Bimatoprost (Lumigan™), Surv Ophthalmol 45 (Suppl 4):S347-S351 (2001); and Woodward et al., The Pharmacology of Bimatoprost (Lumigan™), Surv Ophthalmol 45 (Suppl 4) S337-S345 (2001).
Bimatoprost is an analog (e.g., a structural derivative) of a naturally occurring prostamide. Bimatoprost's chemical name is (Z)-7-[(1R,2R,3R,5S)-3,5-Dihydroxy-2-[1E,3S)-3-hydroxy-5-phenyl-1-pentenyl]cyclopentyl]-5-N-ethylheptenamide, and it has a molecular weight of 415.58. Its molecular formula is C25H37NO4. Bimatoprost is available in a topical ophthalmic solution under the tradename Lumigan® (Allergan, Inc.). Each mL of the solution contains 0.3 mg of bimatoprost as the active agent, 0.05 mg of benzalkonium chloride (BAK) as a preservative, and sodium chloride, sodium phosphate, dibasic; citric acid; and purified water as inactive agents.
Biocompatible implants for placement in the eye have been disclosed in a number of patents, such as U.S. Pat. Nos. 4,521,210; 4,853,224; 4,997,652; 5,164,188; 5,443,505; 5,501,856; 5,766,242; 5,824,072; 5,869,079; 6,074,661; 6,331,313; 6,369,116; and 6,699,493.
Yamada et al. US Patent Publication 2006/0013859 discuss the subconjunctival injection of gels or liquids capable of forming gels in situ in which a sparingly soluble drug-containing component is contained, in order to form a depot for ocular drug delivery, including delivery of such drugs to the posterior segment of the eye.
It would be advantageous to provide methods using eye implantable drug delivery systems, such as microparticles that are capable of releasing a therapeutic agent, such as a cyclic lipid component, preferably at a sustained or controlled rate for extended periods of time and in amounts with few or no negative side effects. In those cases in which it may provide a possible alternative to topical drug delivery, such a system would automatically release the drug over a period of time, thus reducing concerns with daily patient compliance.